feat: add NIST CSF 2.0 nist_csf field to all 754 cybersecurity skills

Mapped every skill to NIST CSF 2.0 subcategory IDs (GV/ID/PR/DE/RS/RC functions)
based on subdomain and content analysis. Restores 11 skills corrupted during
prior rebase, re-enriching with ATLAS, D3FEND, NIST AI RMF, and CSF 2.0 fields.

All 754 skills now carry structured mappings for all 5 security frameworks:
- MITRE ATT&CK (in tags)
- MITRE ATLAS v5.5 (atlas_techniques)
- MITRE D3FEND v1.3 (d3fend_techniques)
- NIST AI RMF 1.0 (nist_ai_rmf)
- NIST CSF 2.0 (nist_csf)

skills/performing-open-source-intelligence-gathering/SKILL.md

@@ -1,12 +1,24 @@
 ---
 name: performing-open-source-intelligence-gathering
-description: Open Source Intelligence (OSINT) gathering is the first active phase of a red team engagement, where operators collect publicly available information about the target organization to identify attack s
+description: Open Source Intelligence (OSINT) gathering is the first active phase of a red team engagement, where operators
+  collect publicly available information about the target organization to identify attack s
 domain: cybersecurity
 subdomain: red-teaming
-tags: [red-team, adversary-simulation, mitre-attack, exploitation, post-exploitation, osint, reconnaissance]
-version: "1.0"
+tags:
+- red-team
+- adversary-simulation
+- mitre-attack
+- exploitation
+- post-exploitation
+- osint
+- reconnaissance
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- ID.RA-01
+- GV.OV-02
+- DE.AE-07
 ---
 # Performing Open Source Intelligence Gathering